Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

All life on Earth contains amino acids and carbonaceous chondrite meteorites have been suggested as their source at the origin of life on Earth. While many meteoritic amino acids are considered indigenous, deciphering the extent of terrestrial contamination remains an issue. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent the most uncontaminated primitive extraterrestrial material available. Here, the concentrations of amino acids from two particles from different touchdown sites (TD1 and TD2) are reported. The concentrations show that N,N-dimethylglycine (DMG) is the most abundant amino acid in the TD1 particle, but below detection limit in the other. The TD1 particle mineral components indicate it experienced more aqueous alteration. Furthermore, the relationships between the amino acids and the geochemistry suggest that DMG formed on the Ryugu progenitor body during aqueous alteration. The findings highlight the importance of aqueous chemistry for defining the ultimate concentrations of amino acids in primitive extraterrestrial samples.

DOI： 10.1038/s41467-023-37107-6

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Other Link： https://www.nature.com/articles/s41467-023-37107-6

Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/maps.13913

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1111/maps.13913

Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.ijms.2022.116893

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Academy  

DOI： 10.2183/pjab.98.015

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Publishing type：Research paper (scientific journal)   Publisher：Oxford University Press (OUP)  

ABSTRACT

Comets and asteroids have traditionally been separated categories, but main belt comets skew this view, portraying a possible intermediate stage between these two endmembers. Investigating the relationship between these bodies can improve our understanding of the formation and evolution of the Solar System and help to identify potentially interesting parent bodies from within our solar system, for future sample return missions. Furthermore, elucidating the ice-organic-silicate ratios of potential meteorite parent bodies can help to explain the observed isotopic ratios and petrography of meteorite samples. While the ice-organic-silicate ratios of particular bodies have been estimated, there has been no study undertaken which compares different types of bodies in terms of their ice-organic-silicate ratios. Therefore, this study presents a geophysical-chemical mass balance model, to estimate the ice-organic-silicate ratios of comets, main belt comets and asteroids. The results drawn from the model form a diagonal trend upon an ice-organic-silicate ternary diagram, in which comets and main belt comets plot together at generally higher ice contents, with asteroids typically plotting at lower ice contents. However, an overlap between all three body types is observed and supports the scenario in which comets, main belt comets and asteroids are genetically linked.

DOI： 10.1093/mnras/stac1068

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Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

DOI： 10.1029/2021je007052

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021JE007052

Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.carbon.2021.10.009

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Publishing type：Part of collection (book)   Publisher：Springer Singapore  

Mineralogical composition in Andosols in Japan was elucidated to clarify the type and provenance of minerals controlling their ability to retain 137Cs. In fine particles (<20 µm), short-range-ordered minerals were dominant, whereas quartz, mica, and felspars were contained as major crystalline minerals in all the soils investigated. Radiocesium interception potential, a widely used indicator of the ability to retain 137Cs, positively correlated with mica and quartz content while not with K-feldspars. Mica and quartz were linearly correlated, suggesting the similarity in their origins. Isolated fine quartz grains were analyzed for oxygen isotopic ratio (d18O) as an indicator of their provenance. Most of the quartz showed the d18O values of 15-17‰, very close to those in the Gobi Desert, while clearly differentiated those from volcanic origins. These results showed that radiocesium retention ability of Andosols is primarily controlled by the proportion of Asian dust incorporated into volcanic ashes.

DOI： 10.1007/978-981-16-6799-2_16

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

Nickel isotope ratios have traditionally been used as an important tracer in cosmochemistry, and recently, it has gained attention in geochemistry, biochemistry, and environmental sciences with the development of MC-ICP-MS. Purification of Ni before isotope measurement is mandatory for obtaining precise data, which has been commonly achieved with ion-exchange chromatography, employing dimethylglyoxime (DMG) as a chelating agent for Ni. However, it has been pointed out that the use of DMG can adversely affect the isotope measurement due to insufficient Ni recovery and mass bias during measurement caused by the remaining DMG. Ni isolation procedures without the usage of DMG were innovated, but they have disadvantages such as the necessity of complex separation methods, high Ni blank, and matrix-dependent Ni recovery. Here, we present a simple Ni isolation procedure without using DMG but with the aid of oxalic acid along with common inorganic acids, achieving near-complete recovery of Ni with low blanks [0.7 ± 0.3 ng (2SD, n = 4)] only using three ion exchange column steps. To validate our method and strengthen the Ni isotope database of reference materials, 60Ni/58Ni of 20 geological reference materials, covering wide matrix compositions, were measured by MC-ICP-MS using the double-spike method. The results have shown that high recovery of Ni, independent of the sample matrix elements was achieved (98 ± 4%) and the 60Ni/58Ni was measured with a 2SD of 0.006-0.084‰ from samples containing 100-200 ng Ni.

DOI： 10.1016/j.aca.2021.338934

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Publishing type：Research paper (scientific journal)  

<jats:p>The δ<jats:sup>18</jats:sup>O values of submarine vent fluids are controlled by seawater-basalt exchange reactions, temperature of exchange, and to a lesser extent, by phase separation. These variations are translated into the δ<jats:sup>18</jats:sup>O values of submarine hydrothermal fluids between ca. 0 and + 4‰, a range defined by pristine seawater and equilibrium with basalt. Triple oxygen isotope systematics of submarine fluids remains underexplored. Knowing how δ<jats:sup>17</jats:sup>O and δ<jats:sup>18</jats:sup>O change simultaneously during seawater-basalt reaction has a potential to improve i) our understanding of sub-seafloor processes and ii) the rock-based reconstructions of ancient seawater. In this paper, we introduce the first combined δ<jats:sup>17</jats:sup>O-δ<jats:sup>18</jats:sup>O-<jats:sup>87</jats:sup>Sr/<jats:sup>86</jats:sup>Sr dataset measured in fluids collected from several high-temperature smoker- and anhydrite-type vent sites at the Axial Seamount volcano in the eastern Pacific Ocean. This dataset is supplemented by measurements of major, trace element concentrations and pH indicating that the fluids have reacted extensively with basalt. The salinities of these fluids range between 30 and 110% of seawater indicating that phase separation is an important process, potentially affecting their δ<jats:sup>18</jats:sup>O. The <jats:sup>87</jats:sup>Sr/<jats:sup>86</jats:sup>Sr endmember values range between 0.7033 and 0.7039. The zero-Mg endmember δ<jats:sup>18</jats:sup>O values span from -0.9 to + 0.8‰, accompanied by the Δ′<jats:sup>17</jats:sup>O<jats:sub>0.528</jats:sub> values ranging from around 0 to −0.04‰. However, the trajectory at individual site varies. The endmember values of fluids from focused vents exhibit moderate isotope shifts in δ′<jats:sup>18</jats:sup>O up to +0.8‰, and the shifts in Δ′<jats:sup>17</jats:sup>O are small, about −0.01‰. The diffuse anhydrite-type vent sites produce fluids that are significantly more scattered in δ′<jats:sup>18</jats:sup>O—Δ′<jats:sup>17</jats:sup>O space and cannot be explained by simple isothermal seawater-basalt reactions. To explain the observed variations and to provide constraints on more evolved fluids, we compute triple O isotope compositions of fluids using equilibrium calculations of seawater-basalt reaction, including a non-isothermal reaction that exemplifies complex alteration of oceanic crust. Using a Monte-Carlo simulation of the dual-porosity model, we show a range of possible simultaneous triple O and Sr isotope shifts experienced by seawater upon reaction with basalt. We show the possible variability of fluid values, and the causal effects that would normally be undetected with conventional δ<jats:sup>18</jats:sup>O measurements.</jats:p>

DOI： 10.3389/feart.2021.691699

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

DOI： 10.3847/PSJ/abf490

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Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.geoderma.2020.114889

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/rcm.8913

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MARY ANN LIEBERT, INC  

The Hayabusa2 mission successfully collected samples from the asteroid Ryugu last year and will return these to Earth in December 2020. It is anticipated that the samples will enable the analysis of terrestrially uncontaminated organic matter and minerals. Such analyses are in turn expected to elucidate the evolution of organic matter through Solar System history, including the origination and processing of biogenically important molecules, which could have been utilized by the first organisms on Earth. In anticipation, studies have made predictions concerning the properties of Ryugu, including its composition. The spectral characteristics of Ryugu, such as albedo, have been employed to relate the asteroid to members of the carbonaceous chondrite group that have been identified on Earth. However, the recent Hayabusa2 touchdown highlights a disparity between the color of surfaces of displaced platy fragments, indicating a brightening trend for the surface exposed to space compared to that facing into the body. Here we present a mass balance calculation with reference to data from the literature, which indicates that Ryugu may contain a significantly higher abundance of organic matter (likely >50%) than the currently most accepted meteorite analogues. A high organic content may result in high levels of extractable organic matter for the second touchdown site, where the spacecraft sampled freshly exposed material. However, high abundances of insoluble aromatic/graphitic rich organic matter may be present in the first touchdown site, which sampled the surface of Ryugu that had been exposed to space. Moreover, we suggest that the potentially high organic abundance and the rubble-pile nature of Ryugu may originate from the capture of rocky debris by a comet nucleus and subsequent water-organic-mineral interactions and sublimation of water ice.

DOI： 10.1089/ast.2019.2198

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Carbonaceous chondrites contain many abiotic organic compounds, some of which are found in life on Earth. Both the mineral and organic matter phases, of these meteorites, have been affected by aqueous alteration processes. Whilst organic matter is known to be associated with phyllosilicate phases, no such relationship has yet been identified for specific organic compound classes. Furthermore, ongoing sample return missions, Hyabusa 2 and OSIRIS-Rex, are set to return potentially organic rich C-type asteroid samples to the Earth. Consequently, strategies to investigate organic-mineral relationships are required. Here we report spatial data for free/soluble organic matter (FOM/SOM) components (akylimidazole and alkylpyridine homologues) and mineral phases. Low and intermediate molecular weight alkylimidazole homologues are more widely distributed than higher molecular weight members, likely due to their affinity for the aqueous phase. On aqueous alteration of anhydrous mineral phases, transported FOM is adsorbed onto the surface or into the interlayers of the resulting phyllosilicates and thus concentrated and protected from oxidising fluids. Therefore, aiding the delivery of biologically relevant molecules to earth, shortly preceding the origin of life.

DOI： 10.7185/geochemlet.2010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.precamres.2019.105475

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.chemgeo.2019.119312

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Language：English   Publishing type：Research paper (scientific journal)  

&lt;jats:title&gt;Abstract&lt;/jats:title&gt;<br />
&lt;jats:p&gt;New K-Ar ages, major and trace element concentrations, and Sr-Nd-Pb isotope data are presented for Oligocene to recent mafic volcanic rocks from the Ethiopian Plateau, the Main Ethiopian Rift (MER), and the Afar depression. Chronological and geochemical data from this study are combined with previously published data sets to reveal secular variations in magmatism throughout the entire Ethiopian volcanic region. The mafic lavas in these regions show variability in terms of silica-saturation (i.e., alkaline and sub-alkaline series) and extent of differentiation (mafic through intermediate to felsic). The P-T conditions of melting, estimated using the least differentiated basalts, reveal a secular decrease in the mantle potential temperature, from when the flood basalt magmas erupted (up to 1550 °C) to the time of the rift-related magmatism (&amp;lt;1500 °C). Variations in the Sr-Nd-Pb isotopic compositions of the mafic lavas can account for the involvement of multiple end-member components. The relative contributions of these end-member components vary in space and time owing to changes in the thermal condition of the asthenosphere and the thickness of the lithosphere. The evolution of the Ethiopian rift is caused by a transition from plume-driven to plate-driven mantle upwelling, although the present-day mantle beneath the MER and the Afar depression is still warmer than normal asthenosphere.&lt;/jats:p&gt;

DOI： 10.1093/petrology/egz043

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Language：English   Publishing type：Research paper (scientific journal)  

Radiocesium (RCs) is selectively adsorbed on interlayer sites of weathered micaceous minerals, which can reduce the mobility of RCs in soil. Therefore, soils developed from mica-deficient materials (e.g. serpentine soils) may have a higher risk of soil-to-plant transfer of RCs. Soils were collected from three serpentine soil profiles; Udepts in Oeyama, Japan, and Udepts and Udox in Kinabalu, Malaysia. Soil was sampled every 3 cm from 0 to 30 cm depth and sieved to isolate soil particles of ≤20 μm diameter for the assessment of radiocesium interception potential (RIP) after a series of pretreatments. One subset was treated with H2O2 to remove organic matter (OM). Another subset was further treated with hot sodium citrate to remove hydroxy-Al polymers (Al(OH)x). RIPuntreated was <0.4 mol kg-1 whereas mica-K content was <0.02% by weight for ≤20-μm soil particles from Udepts and Udox in Kinabalu, Malaysia, values as low as those of non-micaceous minerals (e.g. kaolinite and smectite). Neither OM nor Al(OH)x removal resulted in a large increase in RIP value for these soils. These results clearly indicated that serpentine soils in Malaysia have very few RCs selective adsorption sites due to the absence of micaceous minerals. In contrast, soil from Udepts in Oeyama, Japan showed average RIPuntreated of 5.6 mol kg-1 and mica-K content of 0.72% by weight for the ≤20-μm particles. Furthermore, the RIP value was significantly increased to an average of 22.5 mol kg-1 after removing both OM and Al(OH)x. These results strongly suggest that weathered micaceous minerals primarily control the ability to retain RCs. These micaceous minerals cannot originate from serpentine minerals, and are probably incorporated as an exotic material, such as Asian dust. This hypothesis is supported by the δ18O value of quartz isolated from the ≤20-μm soil particles from Oeyama, Japan (+16.13‰±0.11‰), very similar to that of Asian dust. In conclusion, serpentine soils in Japan may exhibit a reduced risk of soil-to-plant transfer of RCs due to the historical deposition of Asian dust.

DOI： 10.1016/j.jenvrad.2019.03.028

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Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1111/ggr.12280

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DOI： 10.1038/s41467-019-10832-7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Academy  

DOI： 10.2183/pjab.95.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

Northwest Africa (NWA) 6704 is a unique achondrite characterized by a near-chondritic major element composition with a remarkably intact igneous texture. To investigate the origin of this unique achondrite, we have conducted a combined petrologic, chemical, and 187Re–187Os, O, and Ti isotopic study. The meteorite consists of orthopyroxene megacrysts (En55–57Wo3–4Fs40–42
Fe/Mn = 1.4) up to 1.7 cm in length with finer interstices of olivine (Fa50–53
Fe/Mn = 1.1–2.1), chromite (Cr# ∼ 0.94), awaruite, sulfides, plagioclase (Ab92An5Or3) and merrillite. The results of morphology, lattice orientation analysis, and mineral chemistry indicate that orthopyroxene megacrysts were originally hollow dendrites that most likely crystallized under high super-saturation and super-cooling conditions (1–102 °C/h), whereas the other phases crystallized between branches of the dendrites in the order of awaruite, chromite → olivine → merrillite → plagioclase. In spite of the inferred high super-saturation, the remarkably large size of orthopyroxene can be explained as a result of crystallization from a melt containing a limited number of nuclei that are preserved as orthopyroxene megacryst cores having high Mg# or including vermicular olivine. The Re–Os isotope data for bulk and metal fractions yield an isochron age of 4576 ± 250 Ma, consistent with only limited open system behavior of highly siderophile elements (HSE) since formation. The bulk chemical composition is characterized by broadly chondritic absolute abundances and only weakly fractionated chondrite-normalized patterns for HSE and rare earth elements (REE), together with substantial depletion of highly volatile elements relative to chondrites. The HSE and REE characteristics indicate that the parental melt and its protolith had not undergone significant segregation of metals, sulfides, or silicate minerals. These combined results suggest that a chondritic precursor to NWA 6704 was heated well above its liquidus temperature so that highly volatile elements were lost and the generated melt initially contained few nuclei of relict orthopyroxene, but the melting and subsequent crystallization took place on a timescale too short to allow magmatic differentiation. Such rapid melting and crystallization might occur as a result of impact on an undifferentiated asteroid. The O–Ti isotope systematics (Δ17O = −1.052 ± 0.004, 2 SD
ε50Ti = 2.28 ± 0.23, 2 SD) indicate that the NWA 6704 parent body sampled the same isotopic reservoirs in the solar nebula as the carbonaceous chondrite parent bodies. This is consistent with carbonaceous chondrite-like refractory element abundances and oxygen fugacity (FMQ = −2.6) in NWA 6704. Yet, the Si/Mg ratio of NWA 6704 is remarkably higher than those of carbonaceous chondrites, suggesting significant nebular fractionation of forsterite in its provenance.

DOI： 10.1016/j.gca.2018.04.031

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Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1038/s41598-018-28219-x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

The formation of planetesimals and planetary embryos during the earliest stages of the solar protoplanetary disk largely determined the composition and structure of the terrestrial planets. Within a few million years of the birth of the Solar System, chondrule formation and the accretion of the parent bodies of differentiated achondrites and the terrestrial planets took place in the inner protoplanetary disk(1,2). Here we show that, for chondrules in unequilibrated enstatite chondrites, high-precision Delta O-17 values (where Delta O-17 is the deviation of the delta O-17 value from a terrestrial silicate fractionation line) vary significantly (ranging from -0.49 to + 0.84%) and fall on an array with a steep slope of 1.27 on a three-oxygen-isotope plot. This array can be explained by the reaction between an olivine-rich chondrule melt and an SiO-rich gas derived from vaporized dust and nebular gas. Our study suggests that a large proportion of the building blocks of planetary embryos formed by successive silicate-gas interaction processes: silicate- H2O followed by silicate-SiO interactions under more oxidized and reduced conditions, respectively, within a few million years of the formation of the Solar System.

DOI： 10.1038/s41550-017-0137

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

RATIONALE: The precise determination of Delta'O-17 values in terrestrial material is becoming increasingly important to understand the mass-dependent fractionation processes that cause variations in oxygen isotope ratios. San Carlos olivine is widely used as the reference material for oxygen isotope measurements of terrestrial and extraterrestrial materials. We report new Delta'O-17 values for San Carlos olivine that were independently determined in two different laboratories (Geoscience Center [GZG], University of Gottingen) and Institute for Study of the Earth's Interior [ISEI], Okayama University, Misasa) in direct comparison with VSMOW2 and SLAP2 water standards.
METHODS: The delta O-17 and delta O-18 values of VSMOW2, SLAP2, GISP, and San Carlos olivine were determined relative to reference gas. In both laboratories, water and San Carlos olivine samples were prepared by BrF5 fluorination. In both laboratories, the O-2 released from water and olivine samples was passed through the same purification system and measured using the same mass spectrometer relative to the same reference gas.
RESULTS: In both laboratories, the delta O-17(VSMOW2) and delta O-18 (VSMOW2) scales were slightly compressed with respect to the recommended composition of VSMOW2 and SLAP2. The new Delta'O-17(0.528) value (calculated from the VSMOW2-SLAP2 scaled 6 values) of San Carlos olivine from GZG was -36 +/- 9 ppm and, from ISEI, a value of -40 +/- 7 ppm (1(7 standard deviation) was determined. These values are similar to 50 ppm higher than previously reported from the same laboratories. Possible causes for the observed discrepancies are discussed.
CONCLUSIONS: The results of this study in comparison with previous data from the same laboratories demonstrated that for high accuracy determination of Delta'O-17 values: (i) calibration of the reference gas relative to O-2 released from primary standards (VSMOW2, SLAP2) in the same laboratory is highly recommended, (ii) non-linearity of the mass spectrometer may not only affect delta O-17 and delta O-18 values but also Delta'O-17 values, and (iii) the VSMOW2-SLAP2 scaling should also be applied to analyses of rocks and minerals. Studies that are concerned with small differences in Delta'O-17 at similar delta O-18 values, however, are not affected by non-linearity of the mass spectrometer. Copyright (C) 2016 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.7582

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOIL SCI SOC AMER  

Factors controlling the abilities of Allophanic Andosols (representative of Japanese volcanic ash soils) to retain radiocesium (RCs) were assessed. The hypothesis was that retention is largely controlled by traces of micaceous minerals deposited as components of aeolian dust. The radiocesium interception potentials (RIPs), mica K contents were determined in the 2- to 20- and &lt;2.0-mm particle fractions of 23 soil samples from agricultural fields in areas representative of Japanese Allophanic Andosols. Quartz contents were determined in the 2- to 20-mm particle fractions of the same soil samples. The oxygen isotope ratio (delta O-18) in the quartz isolated from each 2- to 20-mm particle fraction was determined to identify the origin of the quartz in each soil sample. The mean RIP for the 2- to 20- and &lt;2-mm particles was 1.7 +/- 0.8 and 2.6 +/- 1.3 mol kg(-1), respectively, and the mica K contents were 3.2 +/- 1.3 and 3.4 +/- 1.7 g kg(-1), respectively, corresponding to micaceous mineral contents of &lt;5% by mass in each size fraction. In spite of their rather low values, the RIPs and mica K contents in each fraction positively correlated (p &lt; 0.01), indicating that the abilities of the soils to retain RCs were mainly controlled by the micaceous mineral contents. The mica K content was proportional to the quartz content in the &lt;20-mm particles, and the mean delta O-18 in the quartz was + 14.8%, similar to those in fine quartz in Chinese loess. These results strongly indicate that the abilities of Allophanic Andosols to retain RCs are largely controlled by micaceous minerals probably originating in aeolian dust.

DOI： 10.2136/sssaj2015.05.0173

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The U-238-Th-230 internal isochron method has great potential for determining eruption ages of young volcanic materials if the separated groundmass phases have a sufficiently wide range of U/Th ratios. We examined the fractionation behavior of U and Th in aged (i.e., &gt;0.5 Ma) basaltic samples by 6 M hydrochloric acid leaching to evaluate the applicability of acid-leaching treatment for the U-238-Th-230 internal isochron method. Acid leaching of aged basaltic rocks in U-238-U-234-Th-230 secular equilibrium at the bulk-rock scale results in Th-230-U-238 and U-234-U-238 radioactive disequilibria for both leachates and residues. These radioactive disequilibria can be explained by redistribution of Th-234 (parent of U-234) and Th-230 between acid-soluble and acid-resistant phases due to alpha-recoil. The number of Th-230 atoms redistributed by alpha-recoil can be calculated by using a mass conservation equation for U-234 atoms and by the relative amount of recoiled Th-230 and Th-234, the latter proportional to the kinetic energy of the recoiled nuclide. When the fraction of daughter nuclide U-234 remaining in either the residue or leachate, after alpha-recoil redistribution of U-238, is large enough (&gt;95%), the corrected (Th-230/U-238) values of leachate and residue show radioactive equilibria. This result demonstrates that preferential fractionation between U and Th does not occur during acid leaching for basaltic samples if there is no selective etching of the alpha-recoil track. This study implies that acid-leaching can be used in conjunction with the U-238-Th-230 internal isochron method for dating young volcanic rocks by evaluating the degree of the alpha-recoil redistribution of U-234. (C) 2015 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chemgeo.2014.12.025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Oxygen isotope compositions are reported for the first time for the Himalayan metabasites of the Kaghan Valley, Pakistan in this study. The highest metamorphic grades are recorded in the north of the valley, near the India-Asia collision boundary, in the form of high-pressure (HP: Group I) and ultrahigh-pressure (UHP: Group II) eclogites. The rocks show a step-wise decrease in grade from the UHP to HP eclogites and amphibolites. The protoliths of these metabasites were the Permian Panjal Trap basalts (ca. 267 +/- 2.4 Ma), which were emplaced along the northern margin of India when it was part of Gondwana. After the break-up of Gondwana, India drifted northward, subducted beneath Asia and underwent UHP metamorphism during the Eocene (ca. 45 +/- 1.2 Ma). At the regional scale, amphibolites, Group I and II eclogites yielded delta O-18 values of +5.84 and +5.91 parts per thousand, +1.66 to +424 parts per thousand, and -2.25 to +0.76 parts per thousand, respectively, relative to VSMOW. On a more local scale, within a single eclogite body, the delta O-18 values were the lowest (-2.25 to-1.44%.) in the central, the best preserved (least retrograded) parts, and show a systematic increase outward into more retrograded rocks, reaching up to +0.12 parts per thousand. These values are significantly lower than the typical mantle values for basalts of + 5.7 +/- 0.3 parts per thousand. The unusually low or negative delta O-18 values in Group II eclogites potentially resulted from hydrothermal alteration of the protoliths by interactions with meteoric water when the Indian plate was at southern high latitudes (similar to 60 degrees S). The stepwise increase in delta O-18 values, among different eclogite bodies in general and at single outcrop-scales in particular, reflects differing degrees of resetting of the oxygen isotope compositions during exhumation-related retrogression. (C) 2014 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.lithos.2014.09.007

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

This work describes two newly discovered eucrite breccias: three presumably paired meteorites, all named Northwest Africa (NWA) 6105, and NWA 6106. For each meteorite, major- and minor-element compositions of minerals were determined using the electron microprobe. Pyroxene Fe-Mn co-variations and bulk-rock oxygen isotope compositions confirm their classification as eucrites. Variations in mineral compositions and textures are attributed to differences in clast types present (i.e., basaltic or cumulate eucrite). The pyroxene compositions support the hypothesis that samples NWA 6105,1; 6105,2; and 6105,3 are paired polymict eucritic breccias, whereas sample NWA 6106 is a monomict basaltic eucritic breccia. Two-pyroxene geothermometry yields temperatures too low for igneous crystallization. The variation in temperatures among samples suggests that metamorphism occurred prior to brecciation.

DOI： 10.1111/maps.12025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

RATIONALE Oxygen triple isotope compositions give key information for understanding physical processes during isotopic fractionation between the geo-, hydro-, bio-, and atmosphere. For detailed discussion of these topics, it is necessary to determine precise 17O-excess values of terrestrial silicate/oxide minerals with respect to Vienna Standard Mean Ocean Water (VSMOW). METHODS Water was fluorinated in an electrically heated Ni-metal tube into which water and BrF5 were loaded for the quantitative extraction of oxygen. Silicate/oxide minerals were fluorinated by heating with a CO2 laser in an atmosphere of BrF5. The extracted oxygen was purified and isotope ratios of the oxygen triple isotope compositions were determined using a Finnigan MAT253 isotope ratio mass spectrometer. RESULTS The oxygen triple isotope compositions of meteoric water and terrestrial silicate/oxide minerals fall on statistically distinguishable fractionation lines, defined as [ln(d17O?+?1)?=??ln(d18O?+?1)?+??], where ? and ? correspond to the slope and intercept, respectively. The fractionation line for meteoric water has ??=?0.5285?+/-?0.0005 and ??=?0.03?+/-?0.02 parts per thousand and for terrestrial silicate/oxide minerals has ??=?0.5270?+/-?0.0005 and ??=?0.070?+/-?0.005 parts per thousand, at the 95% confidence limit. CONCLUSIONS All the analyzed terrestrial silicate/oxide minerals including internationally accepted reference materials (NBS-28, UWG-2, and San Carlos olivine) have a negative 17O-excess with respect to VSMOW. We propose that it is necessary to specify if the determined d17O values of terrestrial and extraterrestrial samples are expressed as the difference from VSMOW or the terrestrial silicate mineral-corrected value. Copyright (c) 2012 John Wiley & Sons, Ltd.

DOI： 10.1002/rcm.6453

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Dislocation textures of olivine grains and Pb isotopic compositions (Pb-207/Pb-206 and Pb-208/Pb-206) of olivine-hosted melt inclusions in basaltic lavas from three Hawaiian volcanoes (Kilauea, Mauna Loa, and Koolau) were examined. More than 70% of the blocky olivine grains in the studied samples have a regular-shaped dislocation texture with their dislocation densities exceeding 10(6) cm(-2), and can be considered as deformed olivine. The size distribution of blocky olivine grains shows that more than 99% of blocky olivines coarser than 1.2 mm are identified as deformed olivine. These deformed olivine grains are identified as antecrysts, which originally crystallized from previous stages of magmatism in the same shield, followed by plastic deformation prior to entrainment in the erupted host magmas. This study revealed that entrainment of mantle-derived crystallization products by younger batches of magma is an important part of the evolution of magnesium-rich Hawaiian magma. Lead isotopic compositions of melt inclusions hosted in the olivine antecrysts provide information of the evolutionary history of Hawaiian volcanoes which could not have been accessed if only whole rock analyses were carried out. Antecryst-hosted melt inclusions in Kilauea and Koolau lavas demonstrate that the source components in the melting region changed during shield formation. In particular, evidence of interaction of plume-derived melts and upper mantle was observed in the earliest stage of Koolau magmatism. (C) 2012 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2012.07.025

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Language：English   Publisher：WILEY-BLACKWELL  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL ACAD SCIENCES  

Records of micrometeorite collisions at down to submicron scales were discovered on dust grains recovered from near-Earth asteroid 25143 (Itokawa). Because the grains were sampled from very near the surface of the asteroid, by the Hayabusa spacecraft, their surfaces reflect the low-gravity space environment influencing the physical nature of the asteroid exterior. The space environment was examined by description of grain surfaces and asteroidal scenes were reconstructed. Chemical and O isotope compositions of five lithic grains, with diameters near 50 mu m, indicate that the uppermost layer of the rubble-pile-textured Itokawa is largely composed of equilibrated LL-ordinary-chondrite-like material with superimposed effects of collisions. The surfaces of the grains are dominated by fractures, and the fracture planes contain not only sub-mu m-sized craters but also a large number of sub-mu m-to several-mu m-sized adhered particles, some of the latter composed of glass. The size distribution and chemical compositions of the adhered particles, together with the occurrences of the sub-mu m-sized craters, suggest formation by hypervelocity collisions of micrometeorites at down to nm scales, a process expected in the physically hostile environment at an asteroid's surface. We describe impact-related phenomena, ranging in scale from 10(-9) to 10(4) meters, demonstrating the central role played by impact processes in the long-term evolution of planetary bodies. Impact appears to be an important process shaping the exteriors of not only large planetary bodies, such as the moon, but also low-gravity bodies such as asteroids.

DOI： 10.1073/pnas.1116236109

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS LTD  

The oxygen isotope (delta O-18) composition of quartz and the d((060)) values of clay minerals were determined from four pedons of non-allophanic Andosols derived mainly from the Holocene volcanic ash on Yakushima Island. These soils contained considerable amounts of aerosol-sized (1-10 mu m) and coarse (&gt;53 mu m) quartz. The delta O-18 values for the aerosol-sized quartz ranged from 14.7 parts per thousand to 17.4 parts per thousand, which was comparable to or slightly lower than known values for loess-derived Red and Yellow soils on Tanegashima Island located approximately 20 km east of Yakushima Island. The abundance and delta O-18 values of the aerosol-sized quartz indicated that non-allophanic Andosols on Yakushima Island were strongly influenced by aeolian dust. However, the presence of coarse quartz implied that granite-derived materials were also incorporated into non-allophanic Andosols. X-ray diffraction patterns for most clay minerals showed two broad peaks around 0.154 and 0.150 nm, respectively. The d((060)) values confirmed that 2:1-2:1:1 clay minerals consisted of dioctahedral and trioctahedral clay minerals. Since aeolian dust contains little or no coarse quartz and trioctahedral clay minerals, the abundance of coarse quartz and trioctahedral minerals confirmed that the occurrence of non-allophanic Andosols on Yakushima was influenced by biotite-granite, in addition to aeolian dust.

DOI： 10.1080/00380768.2012.672926

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Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1380/jsssj.33.681

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Language：English   Publisher：JAPAN SOC ANALYTICAL CHEMISTRY  

In this review, a new classification of elements based on behavior in hydrofluoric acid (HF) solution is presented for the precise quantitative analysis of each element by inductively coupled plasma mass spectrometry (ICP-MS). The elements are divided into 7 groups: (1) "fluorophile" elements; (2) insoluble fluoride-forming elements; (3) "bromophile" or "iodophile" elements; (4) "oxophile" elements; (5) "aquaphile" elements; (6) bare cation elements; and (7) other elements. Especially, the importance of fluorophile and insoluble fluoride-forming elements in elemental analysis is described. Due to the elemental characteristics, these two groups of elements cannot be dissolved simultaneously in the same solution, and thus cannot be measured together. In addition, coprecipitation of the fluorophile elements with the insoluble fluorides occurs in some conditions and hinders accurate analysis. The peculiar conditions when the coprecipitation occurs are discussed, and the "Al-addition" and "Mg-addition" methods for overcoming these problems are described. In addition, some state-of-the-art analytical techniques in ICP-MS are shown, and future directions of the element analysis are presented.

DOI： 10.2116/analsci.25.1181

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Language：English   Publisher：WILEY-BLACKWELL  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：GEOCHEMICAL SOC JAPAN  

In view of the requirement of a well-characterized and easily available aquatic sediment reference material, a comprehensive analysis comprising of fifty major, minor and trace elements as well as Sr-Nd-Pb-Hf isotopes were carried out in the stream sediment reference material, JSd-1, issued by the Geological Survey of Japan. The data for marine sediment reference material, MAG-1, issued by U.S. Geological Survey is also obtained for comparison. The elements were divided into two groups: Group I and Group II. Elements in Group I form stable soluble ions in HNO3; and those in Group II form soluble oxo- and fluoro-complexes in HF, such as Zr, Nb, Hf, Ta, etc. For Group I, the sample was decomposed with HF in a tetra fluoro ethylene (TFE) bomb at 245 degrees C for 96 hrs with Mg addition. The elemental concentration was measured by quadrupole type inductively coupled plasma source mass spectrometry (ICP-QMS) and sector field type ICP-MS (ICP-SFMS) using isotope dilution-internal standardization (ID-IS) methods. The aliquot of the sample solution was passed through 3-step column chemistry for isotope ratio determination of Pb by Multiple collector (MC) ICP-MS and thermal ionization mass spectrometry (TIMS), and Sr and Nd by TIMS. For Group II elements, the sample was decomposed with H F in a TFE bomb with the same time and temperature settings. Zr, Mo, Sn, Sb and Hf were determined by I D, and Nb and Ta by ID-IS using ICP-QMS. The original JSd-1 powder showed heterogeneity for Group II elements, indicating insufficient pulverization and distribution. Thus, we further pulverized the powder and measured the concentration, which showed improved homogeneity. The aliquot for the re-pulverized powder was passed through 2-step column chemistry, and the Hf isotope ratio was determined by MC-ICP-MS. Thus a new data on the trace elements as well as Sr-Nd-Pb-Hf isotope ratios is provided for JSd-1 and MAG-1 in this paper.

DOI： 10.2343/geochemj.1.0018

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The two parallel loci of recent Hawaiian volcanoes, Kea and Loa, have been regarded as the best targets to interpret the chemical structure of an upwelling mantle plume derived from the lower mantle. Here we show that the Sr-Nd-Hf-Pb isotopic data of the shield-building lavas along the Loa locus form a systematic trend from the main shield stage of Koolau (&gt;2.9 Ma) to the active Loihi volcanoes. During the growth of the Koolau volcano, the dominant material in the melting region successively changed from the proposed KEA, DMK (depleted Makapuu), to EMK (enriched Makapuu) components. The proportion of EMK, dominated by a recycled mafic component, is typified by some Koolau Makapuu-stage and some Lanai lavas. Subsequently, the EMK component decreased and LOIHI component increased toward the Loihi lavas. The temporal coincidence between the episodically elevated magma production rate and the abrupt appearance of the typical Loa-type lavas that is restricted to the last 3 Myr should be linked to magma genesis. We suggest that the abrupt appearance of Loa-type magmatism should be attributed to the transient incorporation of the relatively dense recycled material and surrounding less degassed lower mantle material that accumulated near the core-mantle boundary into the upwelling plume. This episodic involvement could have been trigged by episodic thermal pulses and buoyancy increases in the plume. The continuous appearance of Kea-type lavas during the long history of Hawaiian-chain magmatism and the larger magma volume of Kea-type lavas relative to that of the Loa-type lavas in the last 3 Myr indicate that the Kea locus is closer to the thermal centre of the Hawaiian plume relative to that of the Loa locus. (C) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.epsl.2007.10.035

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DOI： 10.1016/j.gca.2006.06.1183

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Boron isotopic compositions of lavas from three representative Hawaiian shield volcanoes (Kilauea, Mauna Loa, and Koolau) were analyzed by thermal ionization mass spectrometry. The boron isotopic composition of each sample was analyzed twice, once with and once without acid leaching to evaluate the effect of posteruptive boron contamination. Our acid-leaching procedure dissolved glass, olivine, secondary zeolite, and adsorbed boron; this dissolved boron was completely removed from the residue, which was comprised of plagioclase, pyroxenes, and newly formed amorphous silica. We confirmed that an appropriate acid-leaching process can eliminate adsorbed and incorporated boron contamination from all submarine samples without modifying the original B-11/B-10 ratio. On the other hand, when the sample was weathered, i.e., the olivine had an iddingsite rim, B-11/B-10 of the acid-resistant minerals are also modified, thus it is impossible to get the preeruptive B-11/B-10 value from the weathered samples. Through this elimination and evaluation procedure of posteruptive contamination, preeruptive delta(11)B values for the shield lavas are -4.5 to -5.4 parts per thousand for Koolau (N = 8), -3.6 to -4.6 parts per thousand, for Kilauea (N = 11), and -3.0 to -3.8 parts per thousand for Mauna Loa (N = 6).
Historical Kilauea lavas show a systematic temporal trend for B content and Nb/B coupled with other radiogenic isotopic ratios and trace element ratios, at constant delta(11)B, indicating little or no assimilation of crustal materials in these lavas. Uncorrelated B content and delta(11)B in Koolau and Mauna Loa lavas may also indicate little or no effect of crustal assimilation in these lavas. The source of KEA-component (identical to the so-called Kea end member in Hawaiian lavas) of the Hawaiian source mantle, represented by Kilauea, should be derived from lower part of subducted oceanic crust or refractory peridotite in the recycled subducted stab. The systematic trend from Kilauea to Koolau-decreasing delta(11)B coupled with decreasing epsilon Nd as well as increasing Sr-87/Sr-86 and Pb-206/Pb-204-is consistent with involvement of subducted sediment components in the EMK(enriched Makapuu)-component, represented by Makapuu-stage of Koolau lavas. Copyright (C) 2005 Elsevier Ltd.

DOI： 10.1016/j.gca.2005.03.009

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Lithium (Li), boron (B), and lead (Pb) isotopic compositions of glass inclusions in olivine phenocrysts from Hawaiian lavas, (Kilauea Iki, Mauna Loa, and Koolau volcano) were measured by high mass resolution ion probe to search for possible signatures of recycled materials in the Hawaiian plume. In order to measure the isotopic compositions, a set of synthetic glass standards with matrices similar to those of the target glass inclusions was prepared. Isotopic variations among these synthetic standards were produced by additions of spikes, and their isotopic compositions were determined by TIMS. Using this set of standards, correction factors for instrumental mass fractionation for Li, B, and Pb isotope measurement were determined with internal precisions of &lt;1.2%, &lt;1.6%, and &lt;0.8% (2sigma) uncertainties for Li, B, and Pb, respectively.
Twenty-eight glass inclusions were measured after homogenization to eliminate dendritic crystals. These glass inclusions showed isotopic variations from -10.2% to +8.4% for delta(7)Li, from -10.5% to +5.2% for delta(11)B, from 0.7994 to 0.8909 for (207) Pb/Ph-206, and from 1.989 to 2.139 for Pb-208/Pb-206, which are considerably larger than those for whole rocks. This suggests that the Hawaiian lavas are mixtures of melts derived from isotopically distinct sources, and that glass inclusions better preserve information regarding source heterogeneity than do whole rocks. In particular, significantly low delta(7)Li and delta(11)B values for the Mauna Loa and Koolau samples indicate an isotopically "light" Li and B source, perhaps containing recycled materials that experienced dehydration during subduction. The extremely low Pb isotope signature, which corresponds to HIMU, also suggests some contribution from recycled materials to the generation of the Hawaiian magma. Our results suggest that recycled materials, which experienced near-surface alteration and then dehydration during subduction, played an important role in creating geochemical heterogeneity in the Hawaiian lavas. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.chemgeo.2004.08.050

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We have evaluated recovery yields of Zr, Nb, Hf and Ta, which are called high field strength elements (HFSE), in the synthetic Ca-Al-Mg-HF solution system using two different methods: at &lt;70&DEG;C in an ultrasonic-bath (denoted as the ultrasonic method) and at 205&DEG;C using a TFE Teflon(R) bomb (denoted as the bomb method). Full recovery of HFSE into the supernatant HF solution was not achieved in cases where fluorite (CaF2) forms in the precipitate in both methods and sellaite (MgF2) forms in the ultrasonic method. In order to suppress fluorite precipitation, an 'Al-addition method' was developed in which Al solution is added to the sample before decomposition to change the matrix solution to a composition in which no fluorite forms. Using the Al-addition method, HFSE concentrations of Ca-rich materials were analyzed by inductively coupled plasma mass spectrometry (ICP-MS) by an isotope dilution method for Zr and Hf and by a calibration curve method for Nb and Ta. Furthermore, we found isotopic disequilibria of Zr and Hf between sample and spike without Al-addition for Ca-rich samples, and that the Al-addition method was very effective in achieving isotopic equilibria and full recovery of HFSE, resulting in high accuracy in their determination.

DOI： 10.1039/b309948b

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Language：English   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

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DOI： 10.1039/b309948b

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Language：English   Publisher：Japan Aerospace Exploration Agency  

We have participated in the analytical competition related to the sample-return mission, MUSES-C of the ISAS, to be launched in May 2003 and returned in summer 2007. In this competition, we have determined major and trace element abundances and isotopes (as many as possible), both for two powdered samples provided by the ISAS and for chondrules separated from Allende meteorite as an additional demonstration of our high-spatial resolution analytical capabilities for fragment samples. 100 mg of each of the competition samples, 1C and 2C, were split into two fractions of approximately 30 and 70 mg for the determinations of elemental abundances and the isotope analyses, respectively. The bulk concentrations of 55 elements in each 30 mg sample were analyzed by quadruple-type ICP-MS and sector-type ICP-MS with analytical uncertainties better than 10 percent (1 sigma). B, Pb, Li, Rb, Sr, Sm and Nd were successively separated from the remaining 70 mg of each of the samples, using a novel integrated, multi-ion exchange column chemistry approach, and then the isotopes of these elements were successfully determined by TIMS with analytical errors similar to those for analyses of terrestrial samples. The Sr, Nd, Re and Os isotopic compositions were also analyzed using the remaining aliquots of the sample solutions for trace element analyses by ICP-MS. The results obtained in this study indicate that 1C and 2C samples are probably ordinary chondrite and the Allende meteorite, respectively. However, extreme W, Ta and Nb enrichments in the 1C were probably caused by contamination during sample preparation. Furthermore, both of the samples were extensively contaminated by B from the borosilicate glass container in which the samples were delivered. Five chondrules were separated from Allende meteorite and then sliced into three pieces using a dicing saw. The center slices were used to petrographically determine the mineral phases, compositionally map these phases by SEM-EDX, and obtain quantitative major and trace element compositions (30 elements) by SEM-EDX and ion microprobe. The two outer slices, for which sample masses were less than 1 mg, were chemically treated to obtain the bulk trace elements and isotope compositions of the chondrules. For the chondrule slices, 24 trace elements and Sr and Nd isotopic compositions were determined with extremely small analytical uncertainties by ICP-MS and TIMS (for Sr and Nd, respectively). Based on the analytical experience, including this competition, we believe that all of the analyses carried out could have been completed within 50 days if we could have concentrated on this project alone during that 50-day period. In this report, we describe the analytical techniques employed for the powdered samples and the chondrules, and we present all of the results obtained during the approximately 3-month period of the analytical competition.

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DOI： 10.9795/bullgsj.53.479

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Language：English   Publishing type：Part of collection (book)   Publisher：Blackwell Publishing Ltd  

Major and trace-element and Sr, Nd, and Pb isotopic compositions have been determined for Koolau shield lavas and Nuuanu and Wailau landslide deposits, Hawaii. The Koolau shield is composed of older main shield-stage and younger Makapuu-stage lavas. Lavas of the main shield-stage are exposed low in the subaerial Nuuanu Pali and in Nuuanu landslide deposits. Main shield-stage lavas resemble Loa- or Kea-type compositions
they are characterized by lower Ba/Nb, La/Nb, Pb/Nd, Sr/Nb, Nd/Nb, Zr/Nb, and 87Sr/86Sr, and by higher 143Nd/144Nd and 206Pb/204Pb than those of Makapuu-stage lavas (Koolau-type). Sr-Nd-Pb isotope systematics suggest that Koolau shield lavas were generated from at least three endmembers, such as: Enriched Makapuu (EMK), Depleted Makapuu (DMK), and Kea (KEA) components. The proportion of these endmembers successively changed from earlier KEA-dominated to later EMK-dominated. Koolau shield-stage lavas span nearly the entire range of the isotopic compositions reported previously for shield-stage lavas from all Hawaiian islands, and reveal secular changes in the amounts of plume components.

DOI： 10.1029/GM128p0311

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Publisher：Japan Association of Mineralogical Sciences  

DOI： 10.14824/jampeg.2002.0.251.0

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We measured Sr-87/Sr-86 and Nd-143/Nd-144 ratios and carried out analytical test of Sr and Nd isotopic standards for the seven GSJ rock reference samples (hereafter GSJ-RRSs); JA-1, JB-1a, JB-2, JB-3, JG-1a, JGb-1 and JR-1. Our mean values of five separate analyses for the GSJ-RRSs are summarized in Table 1, in agreement with the ranges of previously published data. Our mean values for 87Sr/86Sr ratios of JB-2 and JGb-1 and Nd-143/Nd-144 ratio of JR-1, however, show a slightly large Variation as compared with the other JGS-RRSs. Further data accumulation with specification of split/position number is required to evaluate homogeneity in Sr and Nd isotopic compositions.

DOI： 10.2343/geochemj.32.205

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DOI： 10.11456/shigenchishitsu1992.47.1

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